Systems and methods for detecting physical changes without physical contact

Abstract

Systems and methods are provided for detecting and analyzing changes in a body. For example, a system includes an electric field generator configured to produce an electric field. The system includes an external sensor device configured to detect physical changes in the electric field, where the physical changes affect amplitude and frequency of the electric field. The system includes a quadrature demodulator configured to detect changes of the frequency of the output of the electric field generator. The system includes an amplitude reference source and an amplitude comparison switch configured to detect changes of the amplitude of the output of the electric field generator. The system includes a signal processor configured to analyze the changes of the amplitude and frequency of the output of the electric field generator.

What is claimed: 
     
       1. A system for detecting and analyzing changes in a body, comprising:
 an electric field generator configured to generate an electric field that associates with the body; 
 an external sensor device that sends information to the electric field generator, configured to detect a physical change in the body in the electric field, wherein the physical change causes a frequency change in the electric field; 
 a quadrature demodulator that receives the electric field from the electric field generator, configured to detect the frequency change of the electric field generated by the electric field generator and to produce a detected response that includes a low frequency component and a high frequency component, wherein the quadrature demodulator comprises:
 a resonant circuit configured to produce a quadrature input based on an input of the quadrature demodulator; and 
 a mixer, coupled to the resonant circuit, configured to ( 1 ) mix the input of the quadrature demodulator and the quadrature input and ( 2 ) generate an output of the quadrature demodulator; 
 
 a low pass filter that receives the detected response from the quadrature demodulator, configured to filter out the high frequency component of the detected response to generate a filtered response; and 
 a signal processor that receives the filtered response from the low pass filter, configured to analyze the filtered response. 
 
     
     
       2. The system of  claim 1 , further comprising:
 an amplitude reference source configured to provide an amplitude reference; and 
 an amplitude comparison switch, coupled to the amplitude reference source and the electric field generator, configured to compare the amplitude reference and amplitude of the electric field to generate an amplitude comparison response, 
 wherein the signal processor is further configured to analyze the amplitude comparison response. 
 
     
     
       3. The system of  claim 1 , wherein the signal processor comprises:
 a sample-and-hold circuit configured to sample the filtered response; 
 an analog-to-digital converter (ADC), coupled to the sample-and-hold circuit, configured to digitize an output of the sample-and-hold circuit; and 
 a digital signal processor, coupled to the ADC, configured to analyze an output of the ADC. 
 
     
     
       4. The system of  claim 1 , wherein the resonant circuit comprises:
 a capacitor; 
 an inductor; and 
 a resistor. 
 
     
     
       5. The system of  claim 4 , wherein the capacitor, the inductor, and the resistor are connected in parallel. 
     
     
       6. The system of  claim 1 , wherein the mixer is a balanced mixer. 
     
     
       7. The system of  claim 6 , wherein the balanced mixer is a double balanced mixer. 
     
     
       8. The system of  claim 1 , wherein the electric field generator comprises an oscillator. 
     
     
       9. The system of  claim 8 , wherein the oscillator is an inductor-capacitor tank oscillator. 
     
     
       10. The system of  claim 1 , wherein the external sensor device comprises a plurality of metallic plates. 
     
     
       11. The system of  claim 1 , wherein the external sensor device is configured to change its orientation. 
     
     
       12. The system of  claim 1 , further comprising a display. 
     
     
       13. A method for detecting and analyzing changes in a body, the method comprising:
 generating, by an electric field generator, an electric field that associates with the body; 
 detecting, by an external sensor device, a physical change in the body in the electric field, wherein the physical change affects frequency of the electric field; 
 monitoring and detecting, by a quadrature demodulator, changes in the frequency of the electrical field and producing a detected response with at least a frequency component; 
 generating, by a resonant circuit of the quadrature demodulator, a quadrature input based on an input of the quadrature demodulator; 
 mixing, by a mixer of the quadrature demodulator, the input of the quadrature demodulator and the quadrature input to generate an output of the quadrature demodulator; 
 generating, by a filter, a filtered response based on the frequency component; and 
 analyzing, by a processor, the filtered response for detecting the physical change in the body. 
 
     
     
       14. The method of  claim 13 , further comprising:
 detecting, by the external sensor device, a change in the electric field, wherein the physical change affects amplitude of the electric field; and 
 generating an amplitude comparison by using an amplitude comparison switch to compare the amplitude of the electric field with an amplitude reference from an amplitude reference source. 
 
     
     
       15. The method of  claim 13 , further comprising displaying the physical change in at least the frequency of the electric field. 
     
     
       16. The method of  claim 14 , wherein detecting the physical change in the amplitude of the electric field further comprises comparing the amplitude of the electric field with the amplitude reference produced by the amplitude reference source. 
     
     
       17. The method of  claim 13 , wherein detecting the physical change in the frequency of the electric field further comprises:
 detecting, by the quadrature demodulator, changes of the frequency of the electric field and producing the detected response that includes a low frequency component and a high frequency component; and 
 filtering, by the filter, the high frequency component of the detected response to generate the filtered response. 
 
     
     
       18. A non-transitory computer readable medium storing executable instructions operable for detecting and analyzing a change in a body to cause a processor to perform operations comprising:
 generating, by an electric field generator, an electric field that associates with the body; 
 detecting, by an external sensor device, a physical change in the body in the electric field, wherein the physical change affects frequency of the electric field; 
 monitoring and detecting, by a quadrature demodulator, changes in the frequency of the electrical field and producing a detected response with at least a frequency component; 
 generating, by a resonant circuit, a quadrature input based on an input of the quadrature demodulator; 
 mixing, by a mixer, the input of the quadrature demodulator and the quadrature input; 
 generating, by the mixer, an output of the quadrature demodulator; 
 generating, by a filter, a filtered response based on the frequency component; and 
 analyzing, by a processor, the filtered response for detecting the physical change in the body. 
 
     
     
       19. The non-transitory computer readable medium of  claim 18 , further causes the processor to perform operations comprising:
 detecting, by the external sensor device, a change in the electric field, wherein the physical change affects amplitude of the electric field; and 
 generating an amplitude comparison by using an amplitude comparison switch to compare the amplitude of the electric field with an amplitude reference from an amplitude reference source.